Packages of different types and sizes made of corrugated cardboard, or corrugated paperboard, are used in many different areas to pack and protect different kinds of products.
The manufacturing of these packages is performed in substantially two steps, wherein the first step is to manufacture the corrugated paperboard, or cardboard, which in the end of the first step is cut or trimmed into a substantially flat sheet of corrugate paperboard of a predetermined shape. The sheets of corrugated paperboard may also already in the first step be provided with folding lines, also called grooves or scores, which commonly extend crosswise to the direction of corrugation of the corrugated paperboard. In the second step the corrugated paperboards is transformed to a product, for example a box, by cutting, grooving and folding thereby forming a box of the desired size and shape.
I all existing machines for making corrugated paperboard boxes on the market today, so called folding notches are made in the box blanks of the contemplated box before the folding begins in order to facilitate the precision of the folding. These folding notches are often called grooves, or scores, as stated above, and are placed along the contemplated line around which the panel is to be folded.
The actual folding is accomplished in a so called folding unit by which the box blanks are fed at an even rate. In the folding unit, belts and/or belts comprising shoulders are arranged to force the box blanks to fold along the folding notches.
Folding of box blanks utilizing rods and/or folding belts is an old conventional technique shown in for example U.S. Pat. No. 7,708,679. The problem of these solutions is that the rods and/or the folding belts normally influence the box blank unevenly during the folding process, commonly more at the front end of the box blank, which gives rise to an undesired phenomena known in the art as “fishtailing” which implies a certain undesired skewness between the different portions of the box blank after folding.
In more modern folding units the folding belts have been provided with shoulders which are arranged such that they operate in the centre of the box blank to be folded thereby reducing the problem of fishtailing. To ensure the best effect, the speed of the folding belts comprising shoulders should correspond to the speed of the box blanks such that the shoulder does not slide with respect to the sheet during the process, thereby avoiding friction between the shoulder and the sheet surface which aggravates the final folding result. Even if this solution lessens the problem of “fishtailing” there is still a need for an improved technology to increase the precision and quality of the resulting boxes.